How does the use of a recycled polypropylene matrix influence the performance of flax/polypropylene composites compared to a virgin matrix?

Abstract When manufacturing unidirectional flax/thermoplastic composites by thermocompression, the intrinsic characteristics of the matrix can potentially influence the properties of the composite. The objective of this study is to determine the impact of recycled matrix on the performance of flax/MAPP/PP composite. In this work, three PP matrices, one virgin and two recycled, were used in the manufacture of flax/MAPP/PP composites. By a multi‐scale analysis of the three PP matrices, their characteristics influencing the quality of the composite could be identified. It appears that the length of the polymer chains changes the quality of the interface as a short chain length leads to poor entanglement of PP with MAPP. Additionally, high viscosity lowered dispersion of fiber bundles, however it could be corrected by modifying the process pressure. Finally, the presence of a small amount of PE, as is common in recycled PP, has no significant effect on the mechanical properties of composites.